Manchester united has the qualities of winning the europa league but it is not still certain becoming the champion of the league will go to them. Anything can happen along the line, football can not be predicted and their other good teams that are good to win the europa league too.
There are some strong clubs that played in the europa league as well. I think that your focus must not always be on united. United was most favorites club for now but i think that if you need also try to consider about some important clubs like juventus, arsenal and many more.
In my opinion if any team that played in the europa league have the same chance. Juventus has not yet faced a strong team like juventus. roma, leverkusen, sevilla. I think that these team are underrated team at this moment in europa league.
The fact that if MU has become the most favorite team but let's see how it will be going on when MU meets juventus. That's gonna be a tough game for MU. Beating barcelona didn't mean if MU will take trophy easily.
If the clubs you mentioned meet each other then it will indeed be a difficult match for them, and that meeting is certain if they step into even tighter rounds. Like it or not, they will definitely meet each other because some of the smaller and less favorite clubs fell first in the round of 16. Manchester United are one of the contenders for the title, we knew that even when they met Barcelona in the play-offs and knocked him out. But to say who will be the champion later we have to wait longer, because the round of 16 is not over yet.